1. Field of the Invention
The present invention relates generally to the field of golf club heads and more specifically to a golf club wood-type head having a tensioning device for better energy transfer.
2. Background Art
Golf club wood heads that are made from metal (metal woods) and other more exotic high technology materials have distinct advantages over wooden club heads. Generally wooden golf club heads are less durable, vary in density and hardness and require great expertise through the manufacturing process. Metal and exotic materials woods on the other hand can be replicated consistently from the original design, use strong durable materials and are produced using proven manufacturing processes.
Metal and exotic material woods out-perform wooden clubs because they use harder, stronger materials. The use of these materials enables the weight to be transferred to the club head perimeter thereby stabilizing the club head as it comes into impact with the golf ball. Stabilizing the club head at impact reduces the characteristic oscillations that occur to the club head on the golfer""s down swing, resulting in a more efficient transfer of energy to the golf ball. The increased (more efficient) transfer of energy results in additional ball travel distance. Another benefit from a more stable club head is accuracy. If the club head is more stable at impact, less oscillation will occur during impact. This produces less spin to the golf ball and reduces deflection of the club head resulting in straighter shots.
Over the last decade golf club manufacturers have increased the size of metal wood driver club heads. This has happened for two basic reasons: One, golfers are always searching for ways to hit the golf ball longer and straighter. Larger club heads are more stable during impact and are easier to hit, resulting in consistently longer straighter hits. Two, manufacturing methods have improved, allowing the development of larger metal wood driver club heads utilizing extremely thin wall casting or forgings in the structure and in high performance materials such as titanium.
Regardless of manufacturer, most driver club head weights are within a few grams of each other. Typical driver club head weights will range from approximately 192 grams to 202 grams depending on club length, shaft type and manufacturer specifications. Generally, the club head will remain as a constant in order to provide proper balance, physical and mechanical properties which combine to produce a well performing golf club.
Metal wood (driver) club heads utilize thin wall castings or forgings to achieve their size, shape and weight. The larger the driver club head, the thinner the castings or forgings that are required to produce the intended resulting driver club head.
When a driver club head comes into contact with the golf ball, which is stationary, during the golf swing, the resultant collision, depending on the impact velocity and angle of attack, causes the golf ball to compress on the one hand and the driver club head to deform on the other.
The amount of deformation that occurs to the driver club head during impact with the golf ball depends on, but is not limited to the following criteria:
1. The size of the driver club head;
2. The material used to construct the driver club head;
3. The design and construction of the driver club head;
4. The wall thickness of the driver club head;
5. The velocity of the driver club head as it comes into contact with the golf ball;
6. The angle of attack at which the driver club head impacts the golf ball;
7. The distribution of mass within the club head;
8. The mass (weight) of the club head;
9. The stiffness of the club head structure;
10. The strength of the club head structure.
As driver club heads become larger, their ability to prevent deformation at impact with the golf ball becomes more difficult. Even with the use of high performance materials such as titanium or carbon fiber, the weight constraints common in most driver club heads make it imperative to design driver club heads using thin walls. As the driver club head comes into contact with the stationary golf ball during the downswing, the driver club head will oscillate and deform in an effort to find its way around the stationary golf ball. The golf ball compresses under the load during said impact with the club head initiating a lateral direction change of the golf ball away from the center of gravity of the club head resulting in the golf ball rolling in the direction of least resistance prior to the initiation of the rebound phase of the golf ball during impact with the club head. During this impact process, the stored energy that normally would be directed from the driver club head to the golf ball is momentarily redirected to the driver club head. The resulting redirection of energy transfer causes the driver club head structure to flex and deform. This occurrence constitutes a loss of energy that could be imparted from the driver club head to the golf ball. The resulting loss of energy from the driver club head to the golf ball during impact will result in a reduction of energy that can be transferred from the club head to the golf ball resulting in a loss of distance that the golf ball will travel.
The present invention comprises an improved golf driver club head wherein each driver club head has a tensioning device which places the peripheral/outer structure of the metal wood club head in compression thereby resulting in a stronger more rigid metal wood club head structure.
This is accomplished by affixing the tensioning device to the crown (top) surface of the metal wood club head and to the sole (bottom) surface of the metal wood club head. The device is affixed to the two surfaces of the metal wood club head and is pre-tensioned. The tensioning is accomplished by compressing the two metal wood club head surfaces together then affixing the device to the opposed surfaces so that the surfaces are held in state of relative compression. Another way this can be accomplished is to affix the device to the two metal wood club head surfaces either through a hole or boss and to adjust the device by compressing, rotating (screwing), gluing or other form of fastening.
In the preferred embodiment illustrated herein by way of example, the tensioning device comprises an elongated cylindrical member having respective end members. The top and bottom surfaces of the golf club head are each provided with a cylindrical depression or recess and an aperture or passage at the lower end of the depression. The passages are just large enough to accommodate the tensioning device, but are too small to pass the respective end members. During club head manufacture, the length of the device is selected to apply a compressive force between the head surfaces which may preferably be in the range of one pound to three hundred pounds. The actual compression force may be selected to yield the best performance depending on the actual geometry, structure and material of the club head.
While the applicant is not the first to recognize the potential positive effect of a tensioned golf club head (see for example, prior art U.S. Pat. No. 5,501,453), applicant is believed to be the first to employ a tensioning device within the head cavity and the first to compress the top and bottom head surfaces toward one another to resist their further separation during ball impact.
It is therefore a principal object of the present invention to provide a metal wood golf club head having a tensioning device to resist expansion between the top and bottom surfaces of the head during impact with the golf ball.
It is another object of the invention to provide a metal wood golf club head having a tensioning device positioned inside the head for compressing the top and bottom head surfaces in the nominal condition of the club head.
It is yet another object of the invention to interconnect the interior top and bottom surfaces of a metal wood golf club head by a tensioning wire which resists separation of those surfaces during ball impact.
It is still another object of the invention to provide a method for compressing two opposing walls of a golf club metal wood head toward each other to resist their further separation at ball impact.
It is still another object of the invention to improve the performance of a golf club having a metal wood head by employing a tensioning device to compress two opposing walls of the head and thereby resist deformation of the head at ball impact.